I have had Cory's in the past for as long as 10 years. I upgraded to a 20 gal
long tank 8 months ago. I planted it with java fern, sword plants, anubias (blooming now).Java fern on driftwood I boiled then soaked. My paleatus went on a breeding frenzy and lasted 3 months. They laid eggs on the tank but no survivors. Any other species of Cory dies within 2-3 days of being in the tank. This is new and has been going on for a month. At first I thought it was the stock so switched species. Could this be lack of oxygen at the bottom even with a Koralia Nano powerhead (may take out as it may be too much current for C.pygmaeus). Should I add a bubble wand?
1~What type of fish is afflicted? Corydora's only. They eat well the first day then start swimming to the top and sinking down to the gravel by the second. They then swim on their side and struggle to go to the surface before dying.
2~What are your tank parameters (ammonia, nitrites, nitrates, temp, pH)? Ammonia 0, Nitrites 0, Nitrates 0, pH 7.4 using a 2 month old API Freshwater master test kit. Eerily too good? I'm a former microbiologist so I am very careful with testing.
3~ How large is the tank? 20 gal
long How long has the tank been set up? 8 months
4~What type of filtration are you using? 2 AquaClear BOT power filters for 5-20 gallons, 100 gph
5~How many fish are in the tank? 5 Gold Pristella (all less than 1 inch), 3 Rummynose Tetra (small), 8 Cory pygmaeus (less than 1 inch) , 3 Cory sterbai (new to tank)
6~When is the last time you did a water change and vacuum the gravel? 24 hours ago How often do you do this? Water change every week, gravel vacuum every 2 weeks. How much water do you remove at a time? 25-30%
7~How long have you had the fish? Pristella and rummynose about 2 months, C. pygmaeus 1 month. C. sterbai 2 days.
If the fish is new, how did you acclimate it/them? Floated the bag with the fish for 15-20 min in the tank, opened the bag, folded down the top of the bag for the air pocket, added 6 oz tank water, waited 10 min, repeated 2-3 times, removed some water from the bag and repeated 2 times, removed most of the water from bag, poured water and fish into a dedicated container, then netted the fish and put them in the tank.
8~Have you added anything new to the tank--decor, new dechlorinator, new substrate, etc.? No
9~What kind of food have you been feeding your fish, have you changed their diet recently? Hikari Tropical Micropellets, Freeze dried Bloodworms, Tetra Tropical granules, Tetra min tablets, Omega One Shrimp pellets (Not ALL at the same time)
I am at a loss. The local LFS
has checked my water, checked the dead fish, and then declared that I should probably consider other fish than Cory. I kept Cory's in a 10 gal
with painted gravel, a couple sword plants and Anachris, with a Petsmart brand filter, and an occasional monthly water change. I even moved that tank across country in the back of a van plugged in to an outlet in the car and they lived two more years (total of 8-10 years for the lot). Temp was kept about 70F. I'm really at a loss for what to do next. No signs of bloating or white spots, fuzzy stuff. Just a death spiral dance and it's over.
I would appreciate any help with this situation. Thank you